Did you check out the suggestions by Scott?
Suburban uses 2 separate sets of t-stats....one for electric an done for propane
So even of a t-stat trips/goes bad or component fails the other heat source can still function.
T-stats are under the rubber cover (top left) in outside compartment
'Push to Reset' allows manual reset of Hi Temp T-stat if tripped
Left button is for 120V AC electric
Right button is for 12V DC propane
If t-stat not tripped/no reset..........electric element is probably bad
If t-stat tripped/can reset.........then normal t-stat is probably bad & HI limit will trip again